The statements in this section merely provide background information related to the disclosure and may not constitute prior art.
Sleep is essential for a person's health and well-being according to the National Sleep Foundation. Millions of people, however, get insufficient sleep and even suffer from sleep deprivation. Lack of sleep can negatively impact a person's health, mental state, and general disposition. For example, a sleep-deprived person may experience slowed speech, altered emotional response, memory impairment, etc., and have trouble being creative. Lack of sleep can impact a variety of physiological systems including brain and nervous system, cardiovascular system, metabolic function, and immune system.
Sleep is prompted by natural cycles of activity in a brain and includes two basic states: rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. During sleep, a body cycles between non-REM and REM sleep. Typically, people begin the sleep cycle with a period of non-REM sleep followed by a short period of REM sleep.
The period of NREM sleep includes four stages. A completed cycle of sleep includes a progression through the four stages before REM sleep is attained, and the cycle repeats.
In stage 1 (N1) of NREM sleep, readings show a reduction in activity between wakefulness and stage 1 sleep. Stage 2 (N2) is a period of light sleep during which readings show intermittent peaks and valleys, or positive and negative waves. These waves indicate spontaneous periods of muscle tone mixed with periods of muscle relaxation. Stages 3 (N3) and 4 (N4) are deep sleep stages, with stage 4 being more intense than stage 3. Stages 3 and 4 are also referred to as slow-wave, or delta, sleep.
Slow-wave sleep (SWS) is a distinctive feature of sleep in and mammals. It has been shown that SWS has a restorative role, both mentally and physically, and is also associated with the stabilization of memories for long-term storage. Using memory consolidation occurring during SWS, as the brain transfers memories to long-term storage. Slow-wave sleep and slow wave activity diminishes with age, both in duration and intensity, and this decline correlates with impairments in cognitive performance and in particular memory retrieval.
In support of this observation, when compared to age-matched controls, individuals with mild cognitive impairment (MCI) have reduced slow-wave activity. In addition to cognition, slow-wave sleep appears to play an important role in the regulation of cardiometabolic function. Experimental suppression of SWS has been shown to impair metabolic function. Thus, enhancing slow-wave activity could have many beneficial ramifications.
The following detailed description of certain embodiments of the present invention will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, certain embodiments are shown in the drawings. It should be understood, however, that the present invention is not limited to the arrangements and instrumentality shown in the attached drawings.